Roberta deposited 3,116.92 into savings account with an inteest rate of 3.9% compounded quarterly. About how long will it take for the account to be worth 7,000?

Respuesta :

Answer:

the answer is approximated 83 quarters or 21 years

Explanation:

they key in this question is to take into account the word "compounded quarterly" it means that every quarter there is paid [tex]\frac{0.039}{4}=0.975\%[/tex]. So the process to obtain the answe is as follows:

[tex]3116.92*(1+0.975\%)^{n}=7000[/tex]

note here that n is the number of quarters needed for accumulating 7.000 using an interest rate of 0.975%, so we proceed with the solution

[tex]\frac{7000}{3116.92}=(1+0.975\%)^{n}[/tex]

[tex]log(\frac{7000}{3116.92})=n*log(1+0.975\%)[/tex]

Remember here the property of natural logaritm when you apply it to an exponent.

[tex]\frac{log(\frac{7000}{3116.92} )}{log(1+0.975\%)} =n[/tex]

[tex]n=83.38[/tex]

so the answer is aproximated 83 quarters or 21 years

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